Vulcanization of rubber and products obtained thereby



.Patented Jan. 31, 1939 UNITED STATES VULCANIZATI'ON or RUBBER AND mon- UCTS on'rsmsn 'rnaaanr Robert L. Sibley, Nitro, W. Va., assignor, by

mesne assignments,

to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware No Drawing.

25 Claims.

The present invention relates to new vulcanization accelerators, to a process of vulcanizing rubber and to the vulcanization products ob-. tained with the aid of the said new vulcanization 5 accelerators.

The new and preferred class of rubber vulcanization accelerators comprise the reaction products obtainable by reacting a methylol carbamide with a mercapto-thiazole. 7

As typical examples of a methylol carbamide employed in the preparation of the preferred new class of accelerators are dimethylol carbamide and methylol thiocarbamide. As typical examples of mercapto-thiazoles which are reactive with a methylol carbamide and form therewith the new class of vulcanization accelerators are 2-mercapto-4-methylthiazole, Z-mercapto-benzothiazole, 2-mercapto-naphtha-thiazole, 2-mercapto-fi-nitrobenzothiazole, 2-mercapto-5-chlorbenzothiazole, 2-mercapto-4-methylbenzothiazole and the analogues and equivalents thereof.

The compounds of the present invention may be prepared by reacting varying amounts of a methylol carbamide and a mercapto-thiazole. Pref- 25 erably from one to two molecular proportions of 'mercapto-thiazole are reacted with one molecular proportion of methylol carbamide.

In the preparation of the compounds of the present invention it is believed the reaction takes 3 place either as a direct addition of the reacting components as in a salt formation or as a condensation of the reacting components. Provided the reaction is a condensation with the elimination of water, it is believed the preferred accel- 35 erators may be assigned the following general formula:

NiICHrSC c=x NHR r h where X is a sulfur or. oxygen atom and R is 45 hydrogen, an alkyl, aryl, aralkyl or CI-IzOH radical or the grouping The following specific example is to be underw stood as an illustrative embodiment of the in- 55 vention and not in any sense limitative of the scope thereof.

Example Application March 22', 1935, Serial No. 12.474

molecular proportions of mercapto-benzo-thiazole were placed in a suitable reactor equipped with an agitator and reflux condenser. After refluxing for a convenient period of time, for example 24 to 48 hours, the product so obtained was filtered off, washed with ethyl alcohol and dried. The crude product so obtained melts at substantially 221 to 223 C. (corrected). Further purification of said crude product may be effected by recrystallization from a convenient and suitable solvent, for example pyridine, whereupon a pale yellow solid melting at 231 to 232 C. (corrected) is obtained. Theproduct is also readily soluble in ortho dichlorbenzene.

It is believed the reactions involved in the preparation of the above identified material proceed as follows, although the present invention is not limited to any theory as to the formulation of the reactions involved in the preparation of the new and preferred class of accelerators.

NH: NHCHIOH 1; 0:0 +2 ECHO 0:0

NH! NHCHIOH Nncmon S\ (2) 0:0 2 USE o 8 NHCHISC/ \N 0:0

l S NHCHISC The product obtained as described was incorporated in the usual manner into a rubber stock comprising Parts Pale crepe rubber Zing mridn I 5 Sulfur 3 V Stearic a 1 Reaction product of dimethylol carbamide and mercapto-benzothiazole perature'of 30 pounds of steam pressure per square inch. The tests on the vulcanized rubber g E product follow in Table I. P

1 P n m Table I at: "2 8 v Sulfur 2.5 2.5 iff fi i iai ttsai'a; 3'35 M Mioldiigulsmo i v gy I?e xy%:r?| l nA 6 p a A I u 6: ea t 0d ct of d th carbam de n ti'iitfi $133321 an ii fiargptgbenzo-th fole r 0.50 0.00

mmutes lbs/in. percent 700% The rubber stocks were vulcanized by heating for different periods of time in a press at the temgs; 30 2 5:33 31:3 perature of 20' pounds of steam pressure per 7 square inch. The test results on the cured rub- 430 1018 2000 785 I ber product follow in, Table III.

, Table III The data set forth above show that the new and preferred class of accelerators, for example, M du1us 0f elasticity the reaction product of dimethylol carbamide and Time of Q Tensile at 32$? mercapto-benzo-thiazole possess desirable accel- Smell fik g af tionW. crating properties. Moreover, the above uncured 500%" 700% stock showed no set up or prevulcanization as determined by the Williams Plastometer described A 398 1515 2315 780 by Williams, Industrial and Engineering Chemis- 33 728 2865 4050 780 try for 1924 (vol. 16, page 362see also Krall, ibid, vol. 16, page 922) on heating for 180 minutes it: 3 333; 22?; Z32 at 200 F. a

While the preferred class of materials may be $1: 23 5% i222 2233 $23 employed alone as accelerators, their accelerating action is a k dly increased by p y n t From the data set forth in Table III, it is v w r a i n r o tainin l r rs. s readily apparent that diphenyl guanidine phthalactivators thereof, such for examp e, as p e ate and cyclohexylamine possess desirable actiu e, d r ho tolyl idine, heXa me hy1- vating action when employed in conjunction with 9118 tetramine, S fi b ses, y e amm n a reaction product of a mercaptothiazole and a cyclohexylamine, guanidine salts, for example, 111- methylol carbamide, M Dheny guan i e phthalate d analogues e e- The new and preferred class of accelerators of. As a specific example of t e of organic also exhibit desirable accelerating properties t o en containi g acceleratdrs n conjunction when employed in tread stocks and stocks em. with the new accelerators of the present invenploxing redaimed rubber A5 pe ific examti n a rubber st was mp und d prisples of the use thereof in tread stocks rubber insmixes were compounded comprising:

i Parts st, kC st kD Pale crepe rubber; 100

ts art Zinc ox1de 8 PM D s Stearic acid 0.5 u r -5 b'irltiifitti'liffiiii:"133:2?""3223:' 33 Reaction product of dimethylol carbarnide gjfig g g g and mercapto-benzo-thiazole 0.45 steamacid 3 I 3 Pi t 2 2 Dlphenyl guanldlne R ggti t a n productofdimethylol carbamidoand mercapto-benzothia iole 1 0- 8 The rubber stock so compounded was vulcanized Cyclohexylamin by heating for diiferent periods of time in a press at the temperature of 20 pounds of steam presfzompound-eq stacks werte vulca'mzed 3 f sure per square inch. The tensile and modulus mg m press 5 pressu e o figures obtained on the cured product follow in pounds per Square Inch The test data on the Table. II cured rubber products follow in Table IV.

Table IV Table II J t-$*lt t ciym s.m. Stock tit? atelmfimcf- "tiillli elflif fifiii, l elasticity minutes lbsJin percent in lbs/1n. at elonga- Ten 116 t Ultimate Cure time, mintlons ofg g elonga- 200% 300% 400% utes lbs/in tion, iar

v can 500% 700% 0 00 920 2025 3030 530 n 00 2255 4270' 510 005 2645 p 3005 705 0.5 75 1080 2840 3795 510 see 3305 3800 730 D' 75 2280 4115 490 960 3580 3660 705 0 90 1193 3090 3880 400 I D 90 2340 4050 470 Asfurther specific examples of the use of the g 23% 2 50 preferred class of new materials in con unction The rubber stock so obtained was" vulcanized by heating for different periods of time at the temwith organic nitrogen containing accelerators, th following stocks were compounded:

. invention formaldehyde was reacted with thio-" I 9,145,808 It is shown from the data contained in Table IV that the reaction products of a methylolcarbamide and a mercapto-thiazole such for example as a reaction product of dimethylol carbamide and mercapto-benzo thiazole are strong accelerators when employed in tread stocks and especially strong accelerators when employed in conjunction with organic nitrogen containing accelerators as activators thereof.

As a further specific embodiment of the present yellow solid melting at substantially 204 to 205 0., was incorporated in rubber stocks comprising:

I Stock E Stock F parts parts Pale crepe rubber. 100 100. Zinc oxide 8 8 Sulfur 2. 5 2. 5 Btearic acid 5 5 Reaction product of dimethylol thiocarbamide and mercapto-benzo-thiazole. 1 0 .6 Diphenyl guanidine phthalate 0 5 The compounded rubber stock was vulcanized by heating at different times at the temperature of 30 pounds of stea'm pressure per square inch.

The test data of the cured rubbr product follow in Table V.

Table V Modulus at elasticity Time of {35 2 41- Tensil at Ultimate Stock cure, break in elongation,

minutes 7 lbs./in.' percent 500 percent 700 percent E".-- 30 472 1,615 2025 785 F 30 533 1,988 SM 790 E. 60 534 1,82) 2660 770 r--." to 007 2,215 2060 I 740 From the data hereinbefore set forth, it is apparent that the preferred class of materials constitute an important class of rubber vulcanization accelerators which produce a high quality rubber product when employed alone but are of particular' value when employed in conjunction with a nitrogen containing accelerator as an activator thereof.

The present invention is not limited to the specific examples hereinbefore set forth wherein the preferred accelerators are employed. Other ratios of the compounding ingredients than those mentioned in the examples as well as other well known fillers, pigments and the like may be employed in the production of various types of rubber compounds, and are apparent to those skilled in the art to which this invention pertains. The

claims. i

present invention is limited solely by the following rubber -which i 3 tially one molecular proportion of a compound having the formula NHCHaOH .4. x \NHR carbamide and at least one molecular proportion and not more than two molecular proportions of mercapto-aryl-thlazole of the benzene and naph-' thalene series.

- 3. The process of vulcanizing rubber which comprises heating rubber and sulfur in the pres ence of a rubber vulcanization accelerator comprising a product obtainable by reacting substantially one molecular proportion of dimethylol carbamide and at least one molecular proportion and not more than two molecular proportions of mercapto-benzo-thiazole.

4. The process of vulcanizing rubber which I comprises heating rubber and sulfur in the presence of a rubber vulcanization accelerator comprising a product obtainable by reacting substantially one molecular proportion of dimethylol carbamide and substantially two molecular pro:

portions of mercapto-ben'zo-thiazole.

5. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence. of a rubber vulcanization accelerator comprising a product obtainable by reacting substantially one molecular proportion of dimethylol thiocarbamide and substantially two molecular proportions of mercapto-benzo-thiazole.

' 6. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of a rubber vulcanization accelerator comprising a product obtainable by reacting substantially one molecular proportion of a compound having the formula unomon where X is a member of a group consisting in sulfur and oxygen and R is a member of a group consisting in hydrogen, an allwl, aryl, aralkyl and CHaOH radicals with at least one molecular proportion and not more than two molecular proportions of mercapto-aryl-thiazole of the benzene and naphthalene series, admixed with a nitrogen containing vulcanization accelerator as enactivator thereof. v p L 'l. The process of vulcanizing rubber which comprises heating rubber and sulfur in the pres-' ence of a rubber vulcanization accelerator comprising a product obtainable by reacting substantially one molecular proportion of dimethylol carbamide and at leaston'e molecular proportion and not more than two molecular proportions of mercapto-aryl-thiazole of the benzene and naphthaieneseries, admixed with a nitrogen containing vulcanization accelerator as an activator thereof;

8. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of a rubber vulcanization accelerator comprising a product obtainable by reacting substantially one molecular proportion of dimethylol carbamide and substantially-two molecular proportions of mercapto-benzo-thiazole, admixed with diphenyl guanidine phthalate as an activator thereof.

9. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of a rubber vulcanization accelerator comprising a product obtainable by reacting substantially one molecular proportion of dimethylol thiocarbamide and substantially two molecular proportions of mercapto-benzo-thiazole, admixed with diphenyl guanidine phthalate.

10. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of a rubber vulcanization accelerator comprising a product obtainable by reacting substantially one molecular proportion of dimethylol y. carbamide and substantially two molecular proportions of mercapto-benzo-thiazole, admixed with cyclohexylamine as an activator thereof.

11. A vulcanized rubber comprising the vulcanization product of a rubber stock containing prior to the vulcanization thereof a rubber vulcanization accelerator comprising a product obtainable by reacting substantially one molecular proportion of a compound having the formula.

NHOHlOH NHR where X is a member of a group consisting in sulfur and oxygen and R is a member of a group consisting in hydrogen, an alkyl, aryl, aralkyl and CHzOH radicals and at least one molecular proportion and not more than two molecular proportions of mercapto-aryl-thiazole of the benzene and naphthalene series.

12. A vulcanized rubber comprising the vul-,

canization product of a rubber stock containing prior to the vulcanization thereof a rubber vulcanization product of a rubber stock containing I prior to the vulcanization thereof a rubber vulcanization accelerator comprising a product obtainable by reacting substantially one molecular proportion of dimethylol carbamide and su'bstantially two molecular proportions ofmercapto-' benzo-thiazole.

15. A vulcanized rubber comprising the vulcanization product of a rubber stock containing prior to the vulcanization thereof a rubber vulamaaoe 16. A vulcanized rubber comprising the vulcanization product of a rubber stock containing prior to the vulcanization thereof a rubber vulcanization accelerator comprising a product obtainable by reacting substantially one molecular proportion of a compound having the formula Nncmon NHR where X is a member of a group consisting in sulfur and oxygen and R is a member of a group consisting in hydrogen, an alkyl, aryl, aralkyl and CH2OH radicals with at least one molecular proportion and not, more than two molecular proportions of mercapto-aryl-thiazole of the benzene and napththalene series, admixed with a nitrogen containing vulcanization accelerator as an activator thereof.

17. A vulcanized rubber comprising the vulcanization product of a rubber stock containing prior to the vulcanization thereof a rubber vulcanization accelerator comprising a product obtainable by reacting substantially one molecular proportion of dimethylol carbamide and at least one molecular proportion and not more than two molecular proportions of mercapto-aryl-thiazole of the benzene and naphthalene series, admixed with a nitrogen containing vulcanization accelerator as an activator thereof.

18. A vulcanized rubber comprising the vulcanization product of a rubber stockcontaining prior to the vulcanization thereof a rubber vulcanization accelerator comprising a product obtainable by reacting substantially one. molecular proportion of dimethylol carbamide and substantially two molecular proportions of mercapto-benzo-thiazole, admixed with diphenyl guanidine phthalate as an activator thereof.

19. A vulcanized rubber comprisingthe vulcanization product of a rubber stock containing prior to the vulcanization thereof a rubber vulcanization accelerator comprising a product obtainable by reacting substantially one molecular proportion of dimethylol thiocarbamide and substantially two molecular proportions of mercaptobenzo-thiazole, admixed with diphenyl guanidine phthalate.

20. A vulcanized rubber comprising the vulcanization product of a rubber stock containing prior to the vulcanization thereof a rubber vulcanization accelerator comprising a product obtainable by reacting substantially one molecular proportion of dimethylol carbamide and substantially two molecular proportions of mercaptobenzo-thiazole, admixed with cyclohexylamine as an activator thereof.

21. A vulcanization accelerator possessing the structural formula NHCHaSC 22. A-vulcanization accelerator possessing the structural formula s /N11cmsc Nnoms o 23. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of a rubber vulcanization accelerator comprising a product obtainable by reacting substantially one molecular proportion .of a methylol carbamide, the carbonyl carbon atom of which I is directly attached to a sulfur or oxygen atom,

and at least one molecular proportion and not more than two molecular proportions of a mercapto aryl-thiazole or the benzene and naphthalene series.

'24. A vulcanized rubber product comprising the vulcanization product of a rubber stock containing prior to the vulcanization thereof a rubber vulcanization accelerator comprising a product obtainable by reacting substantially one molecular proportion of a methylol carbamide, the carbonylcarbon atom of which is directly attached to a sulfur or oxygen atom, and at least one molecular proportion and not more than two molecular proportions of a mercapto-aryl-thiazole of the benzene and naphthalene series.

25. A vulcanization accelerator possessing the structural formula NHY and R is an arylene radical of the benzene and naphthalene series.

ROBERT L. SIBLEY. 

